Blowholes

When the board temperature is sufficiently raised while passing over the solder wave(s), outgassingcomponents of the board material can lead to blowouts of the still liquid solder. After the solidification of the solder joint, channel- or ball-type deformities may be visible. The most frequent causes for their occurrence are humidity that had been absorbed by the board material, faulty process in the resin system during the board manufacture, or residues from the galvanic process, which are found in cavities of the plated through holes. The latter cause can be the result of the use of dull drills when drilling the through holes.